Lighter than airships and balloons have been known since 1783 when the Montgolfier Brothers Jacques and Joseph made the first successful balloon flight. Ridged airships such as Zeppelins including the Hindenberg, Grafzeppelin, Macon, and Los Angeles differ considerably from blimps and other inflated balloons including hot air balloons. Non-rigid balloons are subject to cracks in the hull envelop which can run a considerable distance and cause the balloon or blimp to crash because the pressure mechanism for maintaining the balloon in flight is insufficient to overcome the leakage caused by the sever crack. Present blimps such as the Goodyear, Sony and Met-Life blimps are limited by regulations to about 150 to 170 feet in length due to the problem of cracks appearing in the hull envelop. A blimp under 170 feet may develop a crack but the safety factor is such that the blimp can land in a short period of time without a catastrophe occurring.
If blimps can be constructed of eight hundred feet or more in length, they can easily transport loads of a million pounds or more very economically and a substantial cost reduction from present fixed winged aircraft. Lighter than air transports can travel much greater distances than present jet fuel aircraft while burning substantially less fuel. Such large non-rigid aircraft can travel faster than cargo carrying ships.
Achieving safety in flight and durability has always been a difficult challenge in pressurized aircraft including fixed wing air vehicles such as modern jets with their pressurized cabins as well as pressure stabilized airships like blimps.
The problems associated with the first commercial jet aircraft, the Comet, are indicative of the hazards of pressurized commercial jets. The energy stored in the pressurized vessel is large, and if a flaw develops, the entire vehicle can be destroyed. Commercial jets have traditionally included bands, (independent of the pressure vessel) that are intended to pick up the load as a crack propagates, and unload the hull material and stop the crack. The Aloa Airlines incident, were a major section of the fuselage left the aircraft, suggests that the method used is marginal.
The airship industry has used a slit coupon test for the last fifty years to ensure the hull material has durability consistent with their purposes. This criteria requires a three inch wide coupon with a one inch wide transverse slit to support a load of three times the design load of the hull. The criteria is empirical in nature and set a standard of safety that was consistent with duty of the intended vehicles. Such vehicles have intended to be used for observation, advertising and light transportation.
As the quest for a more fuel efficient transportation system continues, interest in larger buoyed and semi-buoyed flight mounts. The major stumbling block in the construction of large pressurized stabilized structures is the hull durability issue. Design groups and licensing agencies alike recognize that the current design approaches and licensing criteria are inadequate for large commercial transportation vehicles several hundred feet or more in length and particularly those which run up to eight hundred or one thousand feet.
In present air ships such as blimps, current pressure stabilization is vulnerable to catastrophic deflation from damage of modest size (less than one foot cuts or rips) and are only acceptable to the licensing agencies because of the limited exposure to the general public. Commercial airliner designers have attempted to provide crack stop capability with limited success, but have avoided the safety problems by providing a hull with sufficient strength and life that most damage is minimal and fatigue life is not exhausted before the vehicles are retired. The relatively small size of the fuselage compared to an airship has not at present penalized the vehicles weight to the point of destroying the vehicle's economics.